feat: H0-10 存储空间统计 + 学习资产计数

- GET /users/me/storage（totalBytes/usedBytes/fileCount）
- GET /users/me/assets-summary（kbCount/itemCount/cardCount）

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/modules/users/users.controller.ts

@@ -77,4 +77,18 @@ export class UsersController {
   async removeDevice(@CurrentUser() user: UserPayload, @Param('deviceId') deviceId: string) {
     return this.usersService.removeDevice(String(user.id), deviceId);
   }
+
+  // ── Storage & Assets ──
+
+  @Get('me/storage')
+  @ApiOperation({ summary: '存储空间统计' })
+  async getStorage(@CurrentUser() user: UserPayload) {
+    return this.usersService.getStorage(String(user.id));
+  }
+
+  @Get('me/assets-summary')
+  @ApiOperation({ summary: '学习资产摘要' })
+  async getAssetsSummary(@CurrentUser() user: UserPayload) {
+    return this.usersService.getAssetsSummary(String(user.id));
+  }
 }

src/modules/users/users.service.ts

@@ -68,4 +68,27 @@ export class UsersService {
     });
     return { success: true };
   }
+
+  // ── Storage ──
+
+  async getStorage(userId: string) {
+    const files = await this.prisma.uploadedFile.findMany({
+      where: { userId },
+      select: { sizeBytes: true, mimeType: true },
+    });
+    const usedBytes = files.reduce((sum, f) => sum + f.sizeBytes, 0);
+    const totalBytes = 1024 * 1024 * 1024; // 1GB hardcoded for now
+    return { totalBytes, usedBytes, fileCount: files.length };
+  }
+
+  // ── Assets Summary ──
+
+  async getAssetsSummary(userId: string) {
+    const [kbCount, itemCount, cardCount] = await Promise.all([
+      this.prisma.knowledgeBase.count({ where: { userId, deletedAt: null } }),
+      this.prisma.knowledgeItem.count({ where: { userId, deletedAt: null } }),
+      this.prisma.reviewCard.count({ where: { userId } }),
+    ]);
+    return { knowledgeBaseCount: kbCount, knowledgeItemCount: itemCount, reviewCardCount: cardCount };
+  }
 }